HP D5970A - NetServer - LCII Configuration Manual page 36

Chapter 4
Consider what RAID levels you will need.
Different RAID levels require different minimum numbers of physical
drives. For example, RAID 1 requires exactly two physical drives,
RAID levels 3 and 5 require at least three physical drives, and arrays
with only one physical drive must be assigned RAID 0.
Different RAID levels reserve different amounts of capacity to provide
redundancy.
A single array can be divided into a maximum of eight logical drives.
The integrated HP NetRAID controller can support a maximum of eight
logical drives.
If you want to use the online capacity expansion feature later on, logical
drives cannot span arrays and there must be only one logical drive per
array.
If you want one logical drive to span two or more arrays:
Spanned arrays must be numbered consecutively.
Spanned arrays must contain the same number of physical drives per
array.
Although each physical drive in an array must have the same capacity,
one logical drive can span two or more arrays of different capacities.
For example, one array might contain three drives of 1 GB each, and
the second array might contain three drives of 5 GB each. One logical
drive can span both of these arrays.
As you plan your arrays, it might help to sketch your configuration. See Figures
4-2 and 4-3 for examples.
In Figure 4-2, Logical Drive 1 (labeled "LD1") spans arrays A0 and A1,
occupying space in both. Each array of physical drives is on a separate channel.
30
Planning